Conventionally, there have been known variable displacement vane pumps including vanes contained in slits of a rotor in such a manner that the vanes can be projected therefrom and inserted therein, and configured to change volumes of pump chambers defined among an inner circumferential surface of a cam ring, an outer circumferential surface of the rotor, and the vanes. Japanese Patent Application Public Disclosure No. 2012-87777 discusses one example relating to the above-described technique.